// app.js

const fp = require('lodash/fp');
const _ = require('lodash');
const { Maybe, Container } = require('./supports.js');

// 练习1： 使用fp.add(x, y) 和 fp.map(f, x) 创建一个能让functor 里的值增加的函数ex1
let maybe = Maybe.of([5, 6, 1]);
let ex1 = maybe.map(values => {
    let result = fp.map((val) => {
        let add = fp.add(1);
        return add(val);
    }, values);
    return result;
});
// 简写
// let ex1 = maybe.map(i => fp.map(fp.add(1), i))
console.log('ex1', ex1);

// 练习2：实现一个函数ex2, 能够使用fp.first获取列表的第一个元素

let xs = Container.of(['do', 'ray', 'me', 'fa', 'so', 'la', 'ti', 'do']);

let ex2 = xs.map(values => fp.first(values));
console.log('ex2', ex2);

// 练习3：实现一个函数ex3, 使用safeProp和fp.first找到user的名字和首字母

let safeProp = fp.curry(function (x, o) {
    return Maybe.of(o[x]);
})
let user = { id: 2, name: 'Albert' };
let ex3 = safeProp('name')(user).map(fp.first);
console.log(safeProp('name')(user), ex3);
// 练习4：使用Maybe重写ex4，不要有if语句

// let ex4 = function (n) {
//     if (n) {
//         return parseInt(n);
//     }
// }


let ex4 = function (n) {
    let maybe = Maybe.of(n);
    return maybe.map(value => {
        return parseInt(value);
    });
}

ex4('234');
console.log(ex4(undefined), ex4('234'));